Vapor jet pump



H. G. NDLLER Sept. 11, 1956 VAPOR JET PUMP 3 Sheets-Sheet 1 Filed May28, 1951 INVE/VTUR Sept. 11, 1956 Filed May 28, 1951 H. G. NCLLER VAPORJET PUMP 3 Sheets-Sheet 2 p 11, 1956 H. G. NCLLER 2,762,558

VAPOR JET PUMP Filed May 28, 1951 3 Sheets-Sheet. 3

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. no a H 1\m' Q N Q INVENTOR 0330's 40/19/75 HANS GEO/PG A/O'LLER BY v Vbulk-wax;

ATTORNEY L/TERS/SECOND United States atent VAPOR JET PUMP Hans GeorgNtiller, Koln-Bayental, Germany, assignor to E. Leybolds Nachfolger,Koln-Bayental, Germany, a firm Application May 28, 1951, Serial No.228,555

Claims priority, application GermanyJune 2, 1950 Claims. (Cl. 230-101)The invention relates to pumps, and more particularly to pumps of thevapor jet type wherein the vapor acts as a propellant removing air orsimilar gaseous material to produce .a vacuum.

It is an object of the present invention to provide pumps of the vaporjet type wherein the stream lines of the propellent vapor jet areprevented from diverging excessively and in fact, are caused to extendsubstantially parallel to one another.

Another object of-this invention is to provide vapor .jet type pumpswherein impacts are caused to act at an angle to the jet.

A further object of the invention is to provide vapor jet type pumpswherein the ratio between surface and volume of the-jet-is materiallyincreased.

Still another object of this invention is to provide pumps of the vaporjet type wherein suction output and compression ratio are materiallyincreased.

Other objects, and the manner in which the same are attained, willbecome apparent as this specification proceeds.

Existing vapor jet pumps usingas the propellant, the vapors of mercuryor oil, ;i. e. of high-molecular substances such as hydrocarbons,chlorinated hydrocarbons, high-molecular esters, silicones,-etc.,comprise a vapor jet passing from a nozzle into a bat-He nozzle toproduce a vacuum which is utilized in the removal of I gases or vaporscontained in vessels orotherenclosed spaces connected with the pump. Thegases or vapors which ,as the result of the existence of this vacuum,pass from the vessels or other enclosed spaced into the pump connectedtherewith and expand in the pump, are carried along continuouslyby thevapors discharged from thenozzle-to. pass along, with the said vapors,through the bafile nozzle and into a space wherein the pressureexceedsthatprevailing in the pump proper. The walls of the bafile nzzleprnore otter than not, are cooledwhereby to condensethe vapor andthus increase the vacuum in the pump. It is common knowledge that vaporjetpumpsof the type just described are apt to have a very considerablevoutput.

Tests :as well as theoretical investigations, however, have demonstratedthat with the vapor jet type pumps proposedand made up tonow, theexpansion of the pro pellent vapor .jet proceeds in a manner which hasan unfavorable influence .on the pumping process in that itinvolvesseveralimportant drawbacks. :In the firstplace, the streamlinesof the propellant vapor jet diverge greatly; the compressionimpacts occur ina direction substantially parallel ,to the jet; finally,the surface of,the jet is too small by far by comparison with the volumeof .the jet. In consequence of the drawbacks enumerated above, thesuction output and the compression ratio are materially smaller thanshould be expected on the basis of consideration of energy factors.

The present invention contemplates minimizing the above noted drawbacksof existing vaporjet typepumps, by placing a guide body in the path ofthepropellent vapor jet. In accordance with the invention,1this guide'ice bo y should answer t least som and Pref r bly a o the-followingrequirements: It should be a solid body, it should not be cooled andshould have a contour such that it results in divergence of the streamlines of ,the jet being reduced to a minimum; that one or severalcompression pulses or shock waves (a phenomenon'well known in connectionwith fluids moving at supersonic speeds) act obliquely, or at an anglerelativeto the jet, and that the ratio of jet surface to jet volumeis'increased to a maximum in favor of the former if the d pt o p net aton nt t j o e gas emo d y suction is smallerthan the diameter of thejet.

In the drawings accompanying this specification and form g p he of, seera e o men of th ention are illustrated diagrammatically by way ofexample.

In the drawings,

Fig. 1 is -.a diagrammatical representation including for comparisonpurposes, a basic design to which prior art vapor jet type pumps may 'bereduced;

Fig. 2 is a diagrammatical cross section of one embodiment of thepresent invention;

Figs. 3 and 4, respectively, are similar diagrammatical representations,of two additional embodiments Ofrthfi invention;

F g- :5 s a d a am whe e n t re a i n o suc n speed to suction pressureis plotted in curves for the pumps of the present invention and priorart pumps, respectively.

Fig. 6 is an axialcross-section of a ,rotatiomsymmetrical guide body.

Referring now to the drawing wherein like elements are denoted byidentical reference numerals, and first to Fig. 1, this is adiagrammatical representation of a basic design common to prior artvapor jet type pumps. The vapor jet passes from a .nozzle D into thebafile nozzle K and conveys the gas to be removed by suctionwhich owingto thepressuregradient, passescontinuously from the vessel to beevacuated (not shown) through the connecting pipe S into the spaceR.-through the baflie nozzle K into the space V where the-pressure ishigher than in space R. In pumps of this, prior art, type, however, thejets of propellant issuing from the nozzle diverge greatly so as toexpand, at high velocity, toward the side walls of the baffle K,wherebythe suction output of the pump is materially reduced. This type of pump,manifestly,

displays the other serious drawback that the surface of the jet isrelatively small by comparison with the jet volume.

Referring now to Fig. 2 and the first embodiment of the presentinvention illustrated therein, this shows a guide body E arranged belowthe nozzle D and in the path of the jet issuing therefrom. In theexample illustrated, this guide body E has substantially the form of acone pointing toward the nozzle D, the mantle of the cone being curvedso as to present a concave configuration when viewed in cross-section.The jet issuing from the nozzle so as to have its stream lines extendapproximately parallel, finds in its path the guide body E the contoursof which determine the further course of the jet. In the absence oftheguide body, the stream lines ofthc jet would diverge toward the wallsof the battle being forcedoutwardly-to a very marked degree, whereas theouter stream lines, which diverge considerably by themselves, arecausedto deviate outwardly to the much smaller extentrequired. Thus theguide body E succeeds in causing substantially all stream lines to bedeviated .bylapproxi na lyt s m ansul am n n n c ing any adjacent streamlines to extend in substantially parallel direction.

If the guide body has an outer surface which is strongly curved or bent,such as the mantle of the guide body E which displays sharp bendsindicated at A, the guide body, in addition to the effects noted above,originates oblique shock waves which have their origin at such places asthe sharp bends shown at A.

Moreover, it is manifest that the guide body E is instrumental inincreasing materially the surface of the jet relative to the jet volume,thus improving greatly the ratio between these two factors over theratio existing in the prior art devices.

Experience has taught that in order to arrive at a satisfactoryperformance of a vapor jet pump, the angle formed by the stream lines ofthe jet with the wall of the baflie nozzle, in the vicinity of thiswall, must not'be excessively large. In order to satisfy thisrequirement with the embodiment of the invention where the guide bodycauses the stream lines to deviate materially (e. g. by 90) from theinitial direction of the jet, the inner wall of the pump, in thevicinity of the guide body E, includes a constricted portion Z whichsurrounds the guide body in spaced relation thereto, to extendsubstantially parallel to the bent bottom portion U of the guide body.Thus, with the embodiment of the invention shown in Fig. 2, the bafllenozzle K is formed by guide body E and particularly the lower guideportion U thereof, and by the constricted portion Z in the wall of thepump. The guide body is never cooled, but the wall portion surroundingthe guide body and forming part of the baffle nozzle may -be cooled forthe purpose of condensing the propellant vapor.

In place of the concave guide faces of the guide body shown in Fig. 2,guide faces having other configurations may be adopted. Thus, forexample, the guide faces might be composed of plane and/ or curvedportions or segments so as to resemble a polygon. The only essentialrequirement is that the contours of the guide faces, as a whole, havesome concave curvature and include at least one point where a tangentialplane passing through this point includes with the initial direction ofthe vapor jet, an angle exceeding 15.

According to the embodiment of the invention shown in Fig. 2, thepropellent vapor jet has a circular cross section. A guide bodyaccording to the invention, however, may be used to equal advantage withpumps where the vapor jet has an annular or rectangular cross section,for example. Figs. 3 and 4 illustrate two further embodiments of theinvention where the vapor jets have annular cross sections.

Fig. 3 shows an embodiment of a vapor jet pump having a guide bodyaccording to the invention. Oil evaporated in the evaporating vessel isconveyed through the vapor conduit F, to the nozzle D. Here the oilvapor emerges from an annular slot and in leaving the nozzle D, expandsin the form of an annular jet essentially along the lower guide body Eand the bafiie formed by the cooled wall K. The air to be evacuatedwhich enters the space R through the high vacuum junction S, is carriedalong by the vapor jet and conveyed through the balfle nozzle, into therough vacuum space. The guide body E is so shaped that the stream linesof the vapor jet are aligned to extend substantially parallel to oneanother. For this purpose the vapor jet must be deflected from itsoriginal course by nearly 90, and it is necessary for the cooled wall Kto extend again approximately parallel to the deflected vapor jet. Thecooled wall, therefore, must extend substantially parallel to the bottomportion U of the guide plane E. The wall K and parts disposed below itare cooled by means of the cooling jacket X through which cooling mediumis circulated. To the space V is connected the rough "vacuum pipe Ywhich leads to the rough vacuum pump.

The oil condensed on the cooled walls returns through the return pipe 6into the evaporator 0.

Fig. 4 shows a further embodiment of a vapor jet pump having a guidebody according to the invention. The vapor formed in the heated boiler Oenters the annular space D which at its lower extremity is formed as apropelling nozzle. The wall E serving as guide plane strongly deflectsthe jet from its original course, not outwardly as in the embodiment ofFig. 3, but, on the contrary, inwardly. For this reason the cooled wallK now is disposed in the interior. The cooled wall K is the Wall of thehollow body through which cooling water circulates. The air to beevacuated enters the space R through the high vacuum junction S and inconsequence of its coming in contact with the vapor jet, diffuses intothe propelling jet which conveys it through the annular baffle nozzleformed by the bottom portion U of the guide body and the cooled wall K,into the rough vacuum space V. This space is connected by means of arough vacuum junction Y, with the rough vacuum pump. The oil condensedon the cooled wall is returned through the return pipe G, to theevaporator O. In this embodiment of the invention again the guide planeE is instrumental in rendering the stream lines substantially parallel.

The precise location of the guide body in the path of the vapor jet, ofcourse, depends upon prevailing requirements. Thus, for example, incertain cases the guide body will not be arranged directly below thenozzle as illustrated in Fig. 2, but will be spaced a considerabledistance therefrom.

Fig. 5 illustrates the results of the present invention by a curvedenoted as I showing the relation of suction speed to suction pressure,a similar curve denoted as II being shown to illustrate comparablerelations for a prior art vapor jet pump. The same propelling nozzle wasused in both instances. The numerical values indicated on the suctionoutput curves serve to illustrate the compression ratios atcorresponding pressures.

Fig. 6 is an axial cross-section of a rotation-symmetrical guide body E,the section plane being identical with the axis of symmetry. Its bordercurve includes the straight line U1, the slightly curved line U2 and thestraight line Us. The lines U1, U2 and Us meet at A1 and A2, re-

H spectively, forming kinks which are known, as is also the curve U2, togenerate in supersonic jet compression impulses.

I wish it to be understood that I do not desire to be limited to theexact details of design, construction and operation shown and describedas various modifications well within the scope of the appended claims,may readily suggest themselves to a person skilled in the art.

I claim:

1. A vapor jet pump comprising in combination, a pump casing, a nozzleadapted to emit a vapor jet at supersonic speed, opening into saidcasing, and a guide body adapted to reduce the divergence of adjacentstream lines of said jet, arranged in the path of the jet issuing fromthe nozzle and having an effective guide portion so designed that itscross-section taken along the line of the axis of said nozzle has curvedcontours, the radius of curvature being such that any tangents appliedthereto enclose with the axis of said nozzle, an angle of at least 15,and the crosssection taken at right angles with respect to said nozzleaxis has a contour substantially corresponding to the contour of theopening of said nozzle, said pump casing comprising an interior wallportion extending substantially in parallel and in spaced relationshipto said guide portion.

2. A vapor jet pump according to claim 1, wherein the cross-section ofthe guide portion taken along the line of the axis of the nozzle, hascontours corresponding to a concave curvature.

3. A vapor jet pump according to claim 1, wherein the cross-section ofthe guide portion taken along the line of the axis of the nozzle, haspolygonal contours corresponding, on the whole, to an overall concavecurvature.

4. A vapor jet pump according to claim 1, wherein the cross-section ofthe guide portion taken along the line of the axis of the nozzle, haspolygonal contours including sharp angles whereby to generate shockwaves in the jet impinging thereon.

5. A vapor jet pump according to claim 1, wherein the cross-section ofthe guide portion taken along the line of the axis of the nozzle, hasdiscontinuously curved contours composed of a plurality of segments ofvarying radius of curvature whereby to generate shock waves in the jetimpinging thereon,

References Cited in the file of this patent UNITED STATES PATENTSSchwabach Sept. 3, 1912 Hearing July 15, 1913 Gibson Jan. 18, 1916Carter Nov. 21, 1933 Bancroft July 15, 1941 FOREIGN PATENTS GreatBritain of 1908 Great Britain May 19, 1927 Great Britain Feb. 221, 1947

